ACCUMULATION OF ARSENIC IN THE SHOOTS OF SUDAN GRASS AND BUSH BEAN

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Abstract
When Sudan grass (Sorghum vulgare var. sudanense) and bush bean (Phaseolus vulgaris var. humilis) were grown for varying lengths of time in nutrient solns. containing various concs. of NaAsO2, it was found that concs. of As up to 0.5-0.6 ppm. had no effect on the increase in dry wt. of either plant. Cones. > 1.2 and 12 ppm. of As for bean and Sudan grass, respectively, suppressed growth. The As effected a sudden decrease in the movement of water into the plants as indicated by immediate plasmolysis of roots and wilting of leaves. The concs. of As in the plant tops were proportional to those in the solns. The leaves were highest, the stem tissues intermediate, and the reproductive structures lowest in conc. of As. Within a narrow range of concs. of As in the nutrient medium both plants grew successfully; yet contained concs. of As in their plant tops in excess of the tolerance limit (1.08 ppm. of As) established by law for the As content of foods. For equal relative reductions in yield the more resistant sp. (Sudan grass) contained several times the conc. of As than in the sensitive sp. (bean). Accumulated arsenical residues in soils as a result of insect and weed control practices are discussed as a source of As contamination in foods through absorption by plants.